1. Field of the Invention
The present invention relates to a seat height adjusting device and, in particular, to a device for adjusting the heights of the front and rear portions of a seat cushion of an automotive seat independent of each other or adjusting only the height of the rear portion of the seat cushion.
2. Description of the Prior Art
In a conventional height adjusting device adapted to raise or lower the rear portion of a seat cushion, as shown in FIG. 1, a bell crank (102) supporting the rear portion of a seat cushion frame (101) is connected to an operation knob (103) disposed in the front portion of a seat by means of a link (104) and the front portion of the seat cushion frame (101) is slidably mounted to an upper rail (111) of a seat adjuster (110) via a bracket (112), whereby the rear portion of the seat cushion frame (101) can be moved up or down by rotating the operation knob (103) located in the front portion of the seat. In other words, the rotational movements of the operation knob (103) are converted into horizontal linear displacements by a sector gear (106) intermeshing with a pinion gear (105) which is fixed to a co-axial shaft (107) of the operation knob (103), and then the horizontal linear displacements are converted into vertical linear displacements by means of the bell crank (102), so that the rear portion of the seat cushion frame (101) can be raised or lowered. Also, a shaft (108) for supporting the fan-shaped sector (106) in a fixed manner as well as a crankshaft (109) for supporting the bell crank (102) in a fixed manner are provided so as to extend across the right and left upper rails (111) of the seat adjuster (110).
However, in such a driving system as employs this type of sector gear (106), the sector gear (106) is brought into contact with the femoral region to the bottom of an occupant, which impairs the sitting feeling of the occupant and also may cut or damage a pad. Also, since the driving system is complicated in structure, it is difficult to assemble and may produce loose conditions.